Shrub growth keeps a vicious feedback from enhancing climate change.

Although the climate changes that are being driven by human carbon emissions are likely to cause serious disruptions on their own, one of the additional worries is that the initial warming will set off events that keep changing the planet even if humanity gets its carbon emissions under control. So, for example, warming the oceans could heat up the clathrates that exist there, releasing methane that greatly enhances the greenhouse warming.

The other place that scientists have been watching nervously is the Arctic. About half the carbon stored in the Earth's soil is in the Arctic, where it's locked in place by permafrost and low metabolic activity caused by the cold. As those regions melt, the worry is that bacteria in the soil will start feeding on the carbon trapped there, releasing it into the atmosphere as CO2 that causes further warming.

A new study that looks at 20 years of changes in Alaska, however, suggests that this won't necessarily take place. In the area being studied, the warming temperatures rearranged the ecosystem and redistributed the carbon. But, in the end, there was just as much carbon stored in the soil. What needs to be determined now is just how well this experience will translate to other areas of the Arctic.

To study the impact of the greenhouse effect, scientists set up an actual greenhouse above some tundra in Alaska. Although that works through a completely different mechanism, it has the same sort of effect, warming the soil below it. The greenhouse was put in place back in 1989, and the researchers have spent the decades since tracking the changes that happen in the soil beneath it.

As had been seen at other sites, the warming promoted the growth of woody shrubs—cover rose by a hefty 94 percent. These lead to further warming of the soil by trapping snow in the winter; the snow then acts as an insulator, keeping things warmer than they would be otherwise. However, the researchers found that there was also a short-term summer time warming that persisted for several years as the shrubs were growing.

The plants ended up proliferating at the expense of mosses and lichens, both of which decline precipitously (lichens effectively vanished, with their presence dropping by 99 percent). That shifted the dynamics of the microbial ecosystem in the surface soils. Dead needles from the shrubs break down far more readily than mosses, which increased the speed at which carbon was turned over in the soil. That added warmth also increased the activity of bacteria in the soil, accelerating the decomposition further. The net result was that less carbon ended up stored in the surface soils.

All of that would suggest that initial worries were well founded. But something else happened as a result of the shift to shrubs: root systems began to penetrate far deeper into the soil, and reached depths below the areas that were typically rich in organic matter. And, as the roots penetrated, an ecosystem followed, living off dead roots and organic material that leached from living ones. These microbes eventually attracted more creatures that fed on them, eventually resulting in a significant carbon-based system well below the surface layers.

All told, this deep carbon, combined with the increased storage in the form of shrubs, offset the loss from the surface. The change, in effect, was carbon neutral.

The big remaining question is whether this sort of effect is general. Different shrubs may take over in other regions of the Arctic, and there are some areas that may be perpetually inhospitable to these plants. Nevertheless, if this sort of behavior holds up, then we might be able to breathe a bit easier about the future fate of the Arctic's carbon.

Our lack of understanding about this kind of phenomenon is one of the big limitations in our understanding of climate change. Another is our inability to predict what exactly human beings will add to the atmosphere over the next few decades. Yet another is the lack of an exact understanding of what the impact of any particular volume of new admissions would be. Of course beyond these issues, there is a good possibility that we do not yet understand all of the factors that affect climate change. For systems as complicated as the climate, it is very difficult for any scientist to do the iteration between construction of a model, predictions from the model and measurement of results that is required to refine a model of a complex system and gain confidence in its results. With all the remaining unknowns, that problem becomes even greater because it is hard to control for their possible impacts.

Another typically breathless piece of hysterics and alarmism by ARS, trying to convince us all that there's some huge baby-eating doomsday problem which can only be solved by Communism and that it's getting worser and scarier all the time! </sarcasm>

Carbon feedback isn't the only thing at work, here. Was there a significant albedo change caused by the switch from mosses to shrubs?

As we continue to learn more and more about these processes, as with any field this complex, we also realize how much more there is to learn, and how the real outcomes can be surprisingly different than initial assumptions.

Our lack of understanding about this kind of phenomenon is one of the big limitations in our understanding of climate change.

No the 'limitation' is the Global Warming/Science skeptics who refuse to admit studying something that might be negative is an important priority. They'd rather just believe it's fine and then apparently just deal with the effects. That's great if you're right, but disastrous if you're wrong.

Yet another is the lack of an exact understanding of what the impact of any particular volume of new admissions would be.

Science actually tells us pretty clearly what a volume of CO2 addition to the atmosphere will do., Now, the feedback loops and other things (such as described in this article) certainly have effects that have to be factored in, but the science of what happens when you add CO2 to an atmosphere is rock solid.

For systems as complicated as the climate, it is very difficult for any scientist to do the iteration between construction of a model, predictions from the model and measurement of results that is required to refine a model of a complex system and gain confidence in its results.

It's exactly why you take models and predictions made 30 years ago and compare them to actual results. And what they've found is the models were far too conservative; we've seen effects that were thought to be not possible. So when the current generation models predict really bad effects, you have to believe it's going to be worse. Still warrants study and investigation, but the history suggests are models are too conservative.

And that it's too 'hard' to do? Computers are amazing things especially the super computers that can crunch 100 years of climate in a matter of days or weeks. There's lots of testing and refinement and it's very very doable to make predictions that will be better than previous ones.

Although the climate changes that are being driven by human carbon emissions

way to be unbiased. I am glad you know that the climate is actually changing and that people have caused it.

I'm sorry that you were somehow unaware that, in the science section, we have been consistently biased towards the evidence and the conclusions of the people with the most relevant expertise. Since that's how we handle all the work we cover, i'd assumed it was just obvious.

Setting aside caveat question about whether this scales to the general in the tundra, this is really good news. Good news we could use because of the measured increases of [assumed:methyl hydrate releasing] methane plumes off the shores of Siberia (and iirc Norway?).

Yes, pretty much corroborating what Freeman Dyson and pals found out 50-60 years ago in their own experiments... But it's always nice to see people catching up...!

I wasn't aware Dyson did any Arctic ecology work. Would you care to link to it?

I would guess he is alluding to Oak Ridge Associated Universities (ORAU), a group that coordinated their research programs, and their Energy Analysis program. They did some CO2 research about 30-40 years ago (? roughly?). Dyson didn't really do any work on soils/biology though, that is waaay out of his field. Not sure how much work he even did with on climate at all with Oak Ridge.

ORAU Energy Analysis I do believe had some ideas, and some preliminary data, to do with the feedback loops regarding biology (plants change growth characteristics with changing CO2 concentrations) but I do NOT recall anything that dealt with this specifically, nor really any strong [evidence backed] assertions. Going back 4 decades, it was all pretty primitive compared to now.

There has been some evidence for "greening" of the higher temperate zone latitudes, particularly landlocked areas (AKA Canadian and USSR prairies), via satellite imagery. (EDIT:This is relatively recent, I bet it is mentioned in Ars' archives) But tundra has always been a question mark because its plant suitability was not understood.

I'm guessing WaltC is just being WaltC and tossing contrarian bombs out there.

Downvoting Wheels? Not cool, man. Not cool. Someone needs to get their sarcasm weathervane recalibrated.

So the general idea here is that release of carbon from the surface layers is offset (more than offset?) by increased carbon sequestration in the deeper layers? Does anyone know of any other studies that showed a similar effect? Would it still work like this when permafrost turns to thawed out bog?

Studies like this give me a glimmer of hope that we can actually significantly influence climate change if we reduce emissions now.

Actually, this discovery will undoubtedly be used by Denialists, Inc. as evidence that even if global warming is happening, it won't be as bad as predicted by Al Gore's army of eco-terrorist commies.

Your tone seems to imply that doing so would somehow be wrong. Please, do explain.

I think most (if not all) mainstream climate change prediction do not include the feedback discussed in the article because it was too uncertain to model. Therefore, assuming the conclusions of this local study apply in all regions concerned by the issue, most of the predictions for global warming and associated climate change would remain the same.

This article highlights my problem with the worst case AGW scenarios. If the climate was really that brittle, then the slow and gentle evolution we see in the fossil record could not have happened.

Okay, granted, I can't really make that definitive of a statement. Some evolution would have occurred whatever the climate at any given time. But there must be some safeties and reverse feedbacks built into the natural climate; Otherwise, I don't see how there could be such continuous evolution, with a very slowly changing and constrained climate.

This article highlights my problem with the worst case AGW scenarios. If the climate was really that brittle, then the slow and gentle evolution we see in the fossil record could not have happened.

Okay, granted, I can't really make that definitive of a statement. Some evolution would have occurred whatever the climate at any given time. But there must be some safeties and reverse feedbacks built into the natural climate; Otherwise, I don't see how there could be such continuous evolution, with a very slowly changing and constrained climate.

What you've missed here is that evolution hasn't been slow and gentle, and the climate hasn't been slowly changing and constrained.Paleontologists have recognized for many years that evolution is almost non-existent most of the time, but then it suddenly occurs in large bursts. It used to be called 'punctuated equilibrium', but I don't know if that phrase is still in vogue.Recent core studies have shown that some of the major climate shifts of the past happened over a period of few decades. In other words, the climate really is that brittle.

Science actually tells us pretty clearly what a volume of CO2 addition to the atmosphere will do., Now, the feedback loops and other things (such as described in this article) certainly have effects that have to be factored in, but the science of what happens when you add CO2 to an atmosphere is rock solid.

Yes, and without the feedbacks you mention even double the current level is nothing to worry about. The feedbacks may even dampen the response below the baseline.

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It's exactly why you take models and predictions made 30 years ago and compare them to actual results. And what they've found is the models were far too conservative; we've seen effects that were thought to be not possible. So when the current generation models predict really bad effects, you have to believe it's going to be worse. Still warrants study and investigation, but the history suggests are models are too conservative.

That is complete nonsense.

All these charts are from drroyspencer.com, some of you might be surprised to go there and see his extensive defense of the greenhouse effect. It's simply that like many scientifically literate skeptics, he doesn't believe the IPCC version of climate sensitivity - with good reason.

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And that it's too 'hard' to do? Computers are amazing things especially the super computers that can crunch 100 years of climate in a matter of days or weeks. There's lots of testing and refinement and it's very very doable to make predictions that will be better than previous ones.

And perhaps someday they'll approach a reasonable level of accuracy...

What you've missed here is that evolution hasn't been slow and gentle, and the climate hasn't been slowly changing and constrained....

True, and I'm willing to be wrong; it's more of a feeling at the edge of my awareness of climate change.

To be more precise, it's the "runaway" part that I have a problem with; that there is a tipping point and the ice caps will melt somewhat suddenly. There must be some constraints, otherwise every decent volcano would have ruined the climate and melted the ice caps (if there were any at the time) every time they went off.

Beyond his research, Joshua Schimel (a major author of the nature article) has also written a great book on scientific writing, "Writing Science: How to write papers that get cited and proposals that get funded." Worth a look for anyone working in research. He uses bits from some of his previous work to demonstrate some of the do's and don't's of science writing.

What you've missed here is that evolution hasn't been slow and gentle, and the climate hasn't been slowly changing and constrained....

True, and I'm willing to be wrong; it's more of a feeling at the edge of my awareness of climate change.

To be more precise, it's the "runaway" part that I have a problem with; that there is a tipping point and the ice caps will melt somewhat suddenly. There must be some constraints, otherwise every decent volcano would have ruined the climate and melted the ice caps (if there were any at the time) every time they went off.

I'm not sure why this is being down voted. For me, this is exactly the sort of comment that needs to be encouraged: someone recognizing the limits of their knowledge and asking for more information on the topic. (FWIW, i just added an up vote).

In any case, there are definitely feedbacks that can turn small effects into large ones. The changes in solar forcings that drive the entry and exits into glacial eras are relatively small. If it weren't for feedbacks in terms of greenhouse gasses and ice albedo, not a lot would change. However, there are also limits to the feedbacks - at some point, it simply stops getting warmer/colder.

So, why are we worried about the current climate change: simply because the Earth hasn't seen this much CO2 for millions of years, and we don't know where the limits are in our current context. So, research like this is important, since it gives us a better sense of whether something will be a feedback that changes where the limits are.

To give you a historic analog, during a warmer period around the paleocene-eocene boundary, the orbital cycles drove a series of events called hyperthermals, where the temperatures took an upward excursion of a few degrees, then dropped back to the baseline. But, for one of these, the excursion kept going, CO2 poured into the atmosphere, and the Paleocene-Eocene Thermal Maximum resulted, accompanied by a sub-mass extinction (mostly, ocean life was killed by acidification from all the CO2). Clearly, the hyperthermals had some constraint that simply didn't apply here. And, as far as i can tell, we don't know what was different about this one case.

One way to view this is as a "low probability, high consequence" event. We'll probably hit some limits that keep the feedback from sending things off in a truly awful direction. But we don't know we will, and so we need to a) study potential feedbacks; and b) seriously thinking about doing some planning for the unexpected.

What you've missed here is that evolution hasn't been slow and gentle, and the climate hasn't been slowly changing and constrained....

True, and I'm willing to be wrong; it's more of a feeling at the edge of my awareness of climate change.

To be more precise, it's the "runaway" part that I have a problem with; that there is a tipping point and the ice caps will melt somewhat suddenly. There must be some constraints, otherwise every decent volcano would have ruined the climate and melted the ice caps (if there were any at the time) every time they went off.

There do indeed appear to be tipping points. Although it isn't all of the ice caps that will go at once, for example, but there are very good indications of significant quantum steps. This is important because single steps of the southern cap, for example, can represent very noticeable and impacting changes on ocean levels. For the western cap, for example, the next step is relatively minor but the step past that is enough for a couple meters world-wide rise. A local impact of that around here is that that would come very close to ending the existence of Galveston as an urban area.

EDIT: Remember that some physical systems, for example the solid-liquid boundary of ice, are points of high change. A very small change in temp moves you from solid->liquid (although it happens to also involve a large amount of energy), and the difference in behavior of the matter between solid and liquid states is huge.

It very much does, thank you. I'm curious as to the time spans of those hyperthermals, either duration or in-betweens. Do we have that kind of resolution to have an idea?

The actual resolution of the sediment cores that record them is pretty lousy - it's been compressed for 10s of millions of years. But they do line up with the orbital forcings, and so were probably similar in duration to the current interglacial warm periods, which would be 10-15 thousand years or so. The PETM, in contrast, lasted over 100 thousand years. Once you dump that much carbon into the atmosphere, it takes a hell of a long time to get it all back out again.

It very much does, thank you. I'm curious as to the time spans of those hyperthermals, either duration or in-betweens. Do we have that kind of resolution to have an idea?

The actual resolution of the sediment cores that record them is pretty lousy - it's been compressed for 10s of millions of years. But they do line up with the orbital forcings, and so were probably similar in duration to the current interglacial warm periods, which would be 10-15 thousand years or so. The PETM, in contrast, lasted over 100 thousand years. Once you dump that much carbon into the atmosphere, it takes a hell of a long time to get it all back out again.

Ah. So still big-picture stuff - as far as big CO2 changes over a period of 100 years or so, we're flying blind. Well maybe not blind, but somewhat nearsighted.

Of course, it really doesn't matter. The only viable, long term energy source on the Earth, I believe, is thorium. It gives everybody what they want. It would be nice to see it grow some political legs in my lifetime.

Huh. No flames? The author steps in early and slaps his ruler on the table, and everybody straightens up. Love it. And as to your first thing John ( I hope I can call you John by now ), the voting simply sucks; it has no place here, like it would, say, on a site about Beiber's latest wardrobe. People that want to vote people down, should have to vote them down with words and ideas, not a click and run.

Hopefully we've got a nice big article coming on the IPCCs official report, which is now "real news":

Which I am going to claim is related to this story, as it's a pushback against a climate model. We've known this was coming for a few months (well, my dim awareness) but hopefully John will explore it and speculate why the models are wrong (ish). BBC gets a couple in:

"The researchers say the difference between the lower short-term estimate and the more consistent long-term picture can be explained by the fact that the heat from the last decade has been absorbed into and is being stored by the world's oceans."

"The authors say there are ongoing uncertainties surrounding the role of aerosols in the atmosphere and around the issue of clouds."

I'm a fan of the cloud thing, and I truly think pavement and rooftops are severely undermodeled. The stored ocean heat thing sounds ominous..

Holy crap you are a dick, you just can't help yourself...or you aim for flaming. That post just earned you my first downvote of a post by you. Good job! *shakes head* It is you that is better suited for a site discussing Beeb's wardrobe. LOL